**Colloquium: Thursday, February 27th, 4:25 PM, Lewis Lab 316**

**“****Is There Still Life in Entropy?****”**

Daan Frenkel

University of Cambridge

Entropy is a well-known, but not necessarily well-understood concept. Initially introduced in the context of thermodynamics, it was given a microscopic interpretation by Boltzmann and Gibbs in the context of equilibrium statistical mechanics. But more recently, entropy like quantities have been introduced to describe non-equilibrium systems. For instance, in an attempt to construct a Statistical Mechanics of Powders, Sir Sam Edwards introduced the concept of "granular entropy", defined as the logarithm of the number of distinct packings of N granular particles in a fixed volume V. In 1989, the proposal was rather controversial but much of the debate was sterile because the granular entropy could not even be computed for systems as small as 20 particles - hardly a good approximation of the thermodynamic limit.

In my talk I will describe how granular entropies of much larger systems can now be computed, using a novel algorithm. Interestingly, it turns out the definition of granular entropy will have to be modified to guarantee that granular entropy is extensive. Which brings us back to the Gibbs paradox and a dirty secret of colloid science.

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Physics and Astronomy Colloquia are usually scheduled for Thursdays at 4:25 PM in Lewis Lab room 316. Refreshments and snacks are available in the nearby coffee room at 4:00 PM.

**Physics Colloquium Schedule for Fall 2019**

**Click on Title below for past or upcoming Announcements (where available), and Speaker name for website. ** ** **